The present invention relates to a device for firing a coal-containing, ash-rich sludge produced in a coal-gasifying process by means of a gas-fueled first firebox having an outlet for fume gases, a drier for a fluidized stream of the sludge having an inlet connected to the fume gas outlet of the first firebox to utilize heat energy of the waste gas for drying the fluidized sludge stream, an additional firebox fueld with a dried pulverized sludge and having an outlet for waste gases connected to means for recovering heat energy.
In burning waste sludge generated in a coal-gasifying process it is of uppermost importance to achieve a high degree of combustion, not only for the sake of a high heat yield but also, in the first place, to achieve residual carbon in the ashes of less than 5%, as necessary for utilization of the ashes as a raw material for construction materials. In order to obtain such a high combustion, the firing temperature should be as high as possible. On the other hand, at a high combustion temperature, the ashes liquefy. In order to prevent caking of ashes it is necessary to cool down hot flue gases loaded with ashes before they come into contact with the wall of the firing space.
According to referenced application Ser. No. 390,896, the cooling of fuel gases takes place in the first dust firebox by means of admixing to the fuel gases recirculated waste gas from a drier for a fluidized stream of the sludge. In the second firebox, the waste gas is cooled by feeding fresh air.